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 * Copyright (c) 2005, 2009, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.lang.model.element;

import javax.lang.model.UnknownEntityException;

/**
 * Indicates that an unknown kind of element was encountered.  This
 * can occur if the language evolves and new kinds of elements are
 * added to the {@code Element} hierarchy.  May be thrown by an
 * {@linkplain ElementVisitor element visitor} to indicate that the
 * visitor was created for a prior version of the language.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @see ElementVisitor#visitUnknown
 * @since 1.6
 */
public class UnknownElementException extends UnknownEntityException {

  private static final long serialVersionUID = 269L;

  private transient Element element;
  private transient Object parameter;

  /**
   * Creates a new {@code UnknownElementException}.  The {@code p}
   * parameter may be used to pass in an additional argument with
   * information about the context in which the unknown element was
   * encountered; for example, the visit methods of {@link
   * ElementVisitor} may pass in their additional parameter.
   *
   * @param e the unknown element, may be {@code null}
   * @param p an additional parameter, may be {@code null}
   */
  public UnknownElementException(Element e, Object p) {
    super("Unknown element: " + e);
    element = e;
    this.parameter = p;
  }

  /**
   * Returns the unknown element.
   * The value may be unavailable if this exception has been
   * serialized and then read back in.
   *
   * @return the unknown element, or {@code null} if unavailable
   */
  public Element getUnknownElement() {
    return element;
  }

  /**
   * Returns the additional argument.
   *
   * @return the additional argument
   */
  public Object getArgument() {
    return parameter;
  }
}
